Remove version from Room

We won't need it once we add the per-room lock.

crates/collab/migrations/20221111092550_reconnection_support.sql

@@ -1,6 +1,5 @@
 CREATE TABLE IF NOT EXISTS "rooms" (
     "id" SERIAL PRIMARY KEY,
-    "version" INTEGER NOT NULL,
     "live_kit_room" VARCHAR NOT NULL
 );